Anesthesiology APPLIED Exam › Neuroanesthesia and neuromuscular

Spinal cord injury and autonomic hyperreflexia

Neuroanesthesia and neuromuscular·~5 min read· Physician-reviewed✓ Sourced · 4

Stem

A 34-year-old man, 70 kg, with a complete T4 spinal cord injury from a motorcycle crash three years ago, presents for cystoscopy and laser lithotripsy of a bladder stone. He uses intermittent catheterization and reports episodes of pounding headache and sweating when his bladder is full. Baseline blood pressure is 100/60 and heart rate 64. He says he cannot feel anything below his chest.

Question

He asks why he needs an anesthetic at all. What is your anesthetic plan, and why?

Ideal answer

HeadlineHe needs one: with a lesion above T6, any stimulus below it, usually bladder or bowel, triggers autonomic hyperreflexia.¹ My first choice is a spinal anesthetic.

Spinal, or a general deep enough to suppress the reflex. Blocking the afferent limb prevents it; sedation alone is not enough, and his full-bladder episodes tell me he is prone to it.
No succinylcholine; rocuronium with sugammadex if needed, because his denervated muscle releases enough potassium to arrest the heart.
Arterial line; nitroglycerin or nicardipine drawn up before the cystoscope goes in: with a lesion above T6 and a history of dysreflexia, the surge takes seconds.
Warm actively, measure core temperature, pad every point myself: he is poikilothermic below the lesion, and his skin is insensate, so he cannot tell me it hurts.
Monitor him afterward, because dysreflexia can appear as the anesthetic wears off.

Breaking down the answer

What the reflex is — unopposed sympathetic discharge: severe hypertension, reflex bradycardia and flushing above the lesion.¹ "He cannot feel it" is the trap. The chronic stem, the more common, tests judgment; the acute injury, with spinal shock and an unstable neck, tests adaptability.
Spinal over epidural or general — complete afferent block, my first choice for urologic and perineal surgery; an epidural can spare sacral roots. I accept the scarred back and unpredictable level, and test the block by the pressure response, not sensation.
Succinylcholine after about 48 hours — denervation spreads extrajunctional acetylcholine receptors; the label contraindicates it after the acute phase, risk peaking at 7–10 days with no defined end,² so I avoid it indefinitely. Changes if: first 24–48 hours, still acceptable.
Acute injury: pressure for the cord — hypotension worsens secondary injury. 2013 AANS/CNS: 85–90 mmHg for 7 days; 2024 AO Spine: at least 75–80 mmHg, not above 90–95, for 3–7 days, vasopressor left to the clinician.³
Acute injury: norepinephrine, not crystalloid — a high lesion has lost cardiac sympathetic tone, so phenylephrine alone worsens bradycardia; atropine for the bradycardia. He is vasodilated, not hypovolemic: drowning him in crystalloid is the error.
Acute airway — manual in-line stabilization with the collar front removed, video laryngoscopy or awake fiberoptic if he cooperates; I prepare for bradycardia on laryngoscopy in a cervical lesion.

Follow-up question

The urologist starts under sedation before the spinal is placed. The pressure climbs to 220/120 with a heart rate of 45, and he complains of a pounding headache, his face flushed. What do you do?

Follow-up answer

HeadlineAutonomic dysreflexia. I tell the surgeon to stop and drain the bladder, because removing the trigger is the definitive treatment.¹

I sit him up to pool blood and deepen the anesthetic. If the pressure stays high: nitroglycerin 50–100 mcg or nicardipine 0.5–1 mg IV in increments, or immediate-release nifedipine or nitrate paste without a line; I treat any systolic above 150.⁴ The bradycardia I leave alone: a baroreceptor reflex, it resolves as the pressure falls. Consequences: a 12-lead for ischemia, a neurologic exam for hemorrhage, a chest exam for pulmonary edema. I convert to a spinal or general before surgery resumes and monitor postoperatively, because it recurs with bladder distension on the ward.¹

Pitfalls that cost points

Treating the bradycardia with atropine, which removes the only brake on the pressure.
Choosing labetalol first-line; beta-blockade worsens the bradycardia and the alpha effect is weak.
Stating a succinylcholine window without the mechanism of extrajunctional receptors.

Rapid-fire

Q: Why do lesions above T6 produce dysreflexia and lower lesions rarely do? A: The splanchnic bed, the largest vascular reservoir, is innervated from T5–T9; a lesion above it leaves that vasoconstriction unopposed by descending inhibition.

Q: Why flushing above the lesion and pallor below? A: Baroreceptors trigger compensatory parasympathetic output and vasodilation that can act only above the level of injury.

Q: Why test pulmonary function before an anesthetic in a cervical lesion? A: Vital capacity falls with loss of intercostals, cough is weak, and a C3–C5 lesion compromises the diaphragm; postoperative ventilation is a real possibility.

Q: How long does spinal shock last? A: Flaccidity, areflexia and hypotension for days to weeks, usually 1–3 weeks; spasticity and hyperreflexia follow as the cord recovers reflex activity.

Numbers to know

Item	Value
Lesion level at risk for dysreflexia	T6 and above; about 85% of these patients¹
Succinylcholine	Avoid after 48 hours post-injury; I avoid it permanently
Acute injury MAP goal	At least 75–80, not above 90–95 mmHg, for 3–7 days³
Nitroglycerin	50–100 mcg IV increments or infusion
Nicardipine	0.5–1 mg IV bolus, 5–15 mg/h infusion
Treatment threshold	Systolic above 150 mmHg or symptoms⁴

Sources

1.Autonomic Dysreflexia · OpenAnesthesia (IARS), 2025 · openanesthesia.org
2.QUELICIN (succinylcholine chloride) injection prescribing information · FDA / DailyMed · dailymed.nlm.nih.govContraindicated after the acute phase of upper motor neuron injury; risk peaks at 7-10 days, duration undetermined.
3.A Clinical Practice Guideline on the Timing of Surgical Decompression and Hemodynamic Management of Acute Spinal Cord Injury: Introduction, Rationale, and Scope · AO Spine / Praxis (Global Spine Journal), 2024 · ebi.ac.ukFull text via Europe PMC (PMC10964894); summarizes the 2013 AANS/CNS 85-90 mmHg for 7 days and the 2024 MAP recommendations.
4.Autonomic Dysreflexia wallet card (adult) · Christopher & Dana Reeve Foundation · christopherreeve.orgSit upright; treat systolic above 150 mmHg with a rapid-onset, short-acting agent (nitrate paste, immediate-release nifedipine).

Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.